(ABC News) -- Joan Lunden returned to "Good Morning America" this morning to reveal she has been diagnosed with breast cancer.
"I heard those words that every woman fears and never wants to hear, 'You have breast cancer,'" Lunden told Robin Roberts, also a breast cancer survivor.
Lunden, 63, revealed the breast cancer was found not in her annual mammogram but in a follow-up ultrasound routinely done in addition to the mammogram because Lunden has "dense fibrous tissue."
"Nothing showed in my mammogram and you come out of there like, 'Yes, one more year. I'm okay,'" said Lunden, a mother of seven. "And then you go all happy-go-lucky into the ultrasound and she kept going back to one spot."
Lunden underwent a core biopsy that found what she described as an "aggressive" kind of cancer that will require her to undergo chemotherapy, surgery and radiation, though she is expected to make a full recovery.
"I've got that journey ahead," she said. "I've already started it. I'm already doing my chemo."
Lunden, who co-hosted "GMA" from 1980 to 1997, went on to have a career as a health advocate and says that her position to reach so many women, combined with the legacy of her late father, a cancer surgeon, are what inspired her to come forward with her diagnosis.
"My dad was a cancer surgeon and when I was about 14 he was returning home from speaking at a cancer conference and he was killed in our private plane flying home," Lunden explained. "I always wanted to grow up and be a doctor just like him, because I so admired him."
"The other night I was going to bed and I said, 'You know, if he was looking down right now, he would say, 'All right, you know you've got this and you've lived your life in front of an audience. Use it. Learn everything you can. Impart that information. Go out and try to inspire and maybe save lives. You don't have to be a doctor with a scalpel to maybe change that.'"
"It completely changed my entire frame of how I was looking at it," Lunden said on "GMA." "I went from being a victim to being empowered and having a purpose."
Lunden described her husband, Jeff Konigsberg, as "a rock" and said her family now calls themselves #teamjoan.
"I have just one of the best husbands anyone could ever ask for," Lunden said. "He is there every step of the way and he just gives you so much strength."
"You saw Jamie, Lyndsay and Sarah grow up and they've been with me every appointment," she said of her three older daughters from her first marriage.
Lunden said her two sets of twins - 9-years-old and 11-years-old – were able to get the good news that "Mommy is going to be okay" because she got the diagnosis early on.
"That's really the bottom line," Lunden said. "That you can't be afraid of what you might hear because that's what can really cause you real problems."